Some years have 13 Full Moons, which makes one of them a Blue Moon, as it doesn't quite fit in with the traditional Full Moon naming system.
Today, we use many of these ancient month names as Full Moon names, and many of them come from Colonial Americans adopting Native American names into their calendars.
Although the most commonly used Full Moon names are English interpretations of Native American names, some are also Celtic, Anglo-Saxon, medieval English, and Neo-Pagan.